1. Field of the Invention
The present invention relates to a novel mixed solvent composition belonging to chlorine-free organic solvents, and a method of cleaning various instrument parts using such a solvent and a cleaning apparatus for performing the method.
2. Related Background Art
Chlorofluorocarbons (hereinafter abbreviated as "CFC") have heretofore been used in many industrial fields because most of them are low in toxicity, incombustible and chemically safe, and various kinds of flons different in boiling point are available. Among these, flon 113 has been used as a degreasing solvent or vapor cleaning and drying solvent for many plastic materials, a part of rubber materials and various composite materials, making good use of specific chemical properties inherent in the solvent.
Also, trichloroethane has been used as a replacement for 1,1,2-trichloroethylene and 1,1,2,2-tetrachloroethylene, which have hitherto been used as degreasing and cleaning solvents for metal surfaces after metal working, but are noxious to the human body and are the cause of pollution of underground water.
In recent years, however, ozone holes by which global environment is made worse have been discovered, and the main cause of the ozone hole being formed has been proved to be attributable to organochlorine compounds such as CFC.
For example, flon 113, which is chemically stable, lasts long in the troposphere, diffuses to the stratosphere and is photochemically decomposed by rays of the sun there, thereby generating chlorine radicals which then combine with ozone so as to destroy the ozonosphere.
Therefore, after this, the organochlorine compounds including flons have a tendency for their use to be internationally limited and finally completely prohibited. Among these, flon 113 as described above is high in ozone depletion potential. Thus, it is desirable to replace flon 113 is desired to, and there is a schedule for sharply reducing its use. Trichloroethane is also scheduled to be sharply reduced for the same reason as described above.